I'm back with an update.
Firstly i used the link given by Fredfox to download the firmware and update tool. Unfortunately the firmware flash did not work as the firmware file was not recognised by the update tool. I followed the instructions to the letter. Maybe i did something wrong.
From searching around further i have seen on a few websites that the firmware is not made available to the public. The firmware is only given to ISP's. I have a link to Amazon forum which gives more details. I do not know how to link on these boards and don't want to copy and paste the URL as i don't know if i'll be breaking forum rules so i'll just paste part of the discussion.

"The main problem seems to be that the router server address has to be baked into the firmware. It is not a configurable option. In addition for it to do anything the ISP's server would need to hold a config for your device which by default it would not have because they did not sell it to you and, therefore, do not know the device's serial number or make/model.."

To surmise it looks like unless your ISP has their own firmware for the TG582n and are willing to supply it to you rather than getting you to purchase a router from them then you can unlock it.

I have ordered a new and different router.
Many thanks for all the replies and help. It is all appreciated.
PS. Vivaciti got back to me on Monday and have said there is something wrong with their phone system which is why i couldn't get through on Saturday. Still, you would of thought that the support ticket i opened on Saturday afternoon wouldn't be affected by their phone system!!